Gliederung

Objective: Infections with neurotropic viruses [simian virus 40 (SV40), JC virus (JCV), BK virus (BKV), human papilloma virus (HPV), human cytomegalovirus (HCMV), herpes simplex virus (HSV), Epstein-Barr virus (EBV)] are thought to play a role in the development of primary brain tumors, but the cellular source of positive PCR results in infected tumor tissues remains unclear. In immunodeficient patients, EBV-carrying B-lymphocytes were proposed to be a possible source, but a direct infection of brain resident cells has not been excluded. In this study, we tested different types of primary brain tumors for the appearance of neurotropic viruses and verified an EBV infection in one oligodendroglioma tissue. Here we describe results obtained from our study sample and our attempt to analyze the source of EBV-positive cells to determine the role of EBV infection for tumorigenesis.

Methods: Frozen tumor samples of 55 brain tumor patients (gliomas, meningiomas) were homogenized and genomic DNA was isolated. DNA was tested by nested PCR analysis for the integration of viral sequences from the above mentioned neurotropic viruses. In one patient with EBV-infected tumor tissue, DNA derived from the tumor tissue, the corresponding tumor cell culture and the patient’s blood was analyzed for an EBV sequence. Immunohistochemical staining of frozen tumor tissues and, for positive control, of an EBV-immortalized lymphoblastoid cell line (GCi-LCL) was done using antibodies against the EBV-specific protein LMP1.

Results: While HSV, HCMV, HPV, BKV, JCV and SV40 were not detected in any of the tumor samples, we amplified a viral DNA sequence of the EBV-specific protein EBNA-2 in the tumor tissue of a 53-year-old patient suffering from low-grade oligodendroglioma. High IgG titers against EBV were detected in the patient’s serum and the EBNA-2 sequence was amplified from the tumor tissue and blood cells but not from the corresponding cell culture. In line with these results, immunohistochemical staining of the tumor tissue did not reveal any LMP1 protein expression.

Conclusions: Our data suggest that the infection of brain tissue by neurotropic viruses is an extremely rare event and does not seem to play a significant role in the development of primary brain tumors. For the only patient in our study sample with EBV-infected tumor tissue, we were the first to identify blood cells to be the real source of EBV infection while tumor cells were negative. Therefore future studies should include an analysis of corresponding blood DNA in order to answer the question whether viral infections are involved in tumorigenesis.